1. Field of the Invention
This invention relates to transparent contact lenses for correcting vision deficiencies of the eye. More particularly this invention relates to contact lenses having a central core of a transparent hydrophobic oxygen permeable polymeric material of a uniform, ultrathin coating of a hydrophilic polymeric material integrally bonded to the surface of the hydrophobic material.
2. Description of the Prior Art
Presently, contact lenses can be prepared from optically clear hydrophilic gel materials such as disclosed in U.S. Pat. No. 2,976,576 issued Mar. 28, 1961 of O. Wichterle et al. or from hydrophobic materials such as polymethylmethacrylate.
While the hydrogel lenses of Wichterle et al. are optically satisfactory, have excellent wettability characteristics, and are comfortable on the eye, they are sufficiently oxygen permeable to the extent a patient can suitably wear the lens for a period of time of about 12 hours. The hard contact lenses such as those prepared from polymethylmethacrylate are without any manifestation of oxygen permeability and can be uncomfortable to the wearer because of the lack of wettability and the lack of flexibility. The hardness of the lens causes it to be particularly incompatible with the eye surface.
Soft lenses such as those prepared from polysilicones manifest excellent oxygen permeability. However, the silicone lenses are not wettable and hence, subject the wearer to discomfort.
In order to obtain contact lenses having the characteristics of softness and high oxygen permeability together with wettability it has been suggested that the surface of a silicone core be rendered hydrophilic by treating the surface with a hydrophilic material. U.S. Pat. No. 3,745,042 of Lim et al., issued July 10, 1973, discloses a method of hydrophilizing hydrophobic lenses by coating a hydrophobic lens with a hydrophilic polymerizable hydrophilic monomer, swelling the surface of the lens material in a suitable swelling solvent so as to allow a partial soaking of the hydrophilic material into the hydrophobic material and polymerizing.
U.S. Pat. No. 3,916,033 of Merrill, issued Oct. 28, 1975, discloses a method of grafting a hydrophilic polymer onto the surface of a polysiloxane lens by means of high energy ionizing radiation.
U.S. Pat. No. 3,854,982 of Aelion et al., issued Dec. 17, 1974, discloses a method of hydrophilizing the surface of a hydrophobic substrate by coating the hydrophobic surface with a polymerizable hydrophilic material and irradiating the coated substrate with high energy radiation.
Other patents which disclose methods of hydrophilizing hydrophobic substrates are West German Pat. No. 3,165,805 and U.S. Pat. No 3,350,216 of McVannel et al., issued Oct. 31, 1967, and U.S. Pat. No. 3,854,982 of Aelion, issued Dec. 17, 1974. In each of these methods the control of the hydrophilic thickness is difficult and the hydrophilic surface may not be uniform.